HttpWebRequest 

//body是要传递的参数,格式"roleId=1&uid=2"
//post的cotentType填写:
//"application/x-www-form-urlencoded"
//soap填写:"text/xml; charset=utf-8"
public static string PostHttp(string url, string body, string contentType)
{
HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url);

httpWebRequest.ContentType = contentType;
httpWebRequest.Method = "POST";
httpWebRequest.Timeout = 20000;

byte[] btBodys = Encoding.UTF8.GetBytes(body);
httpWebRequest.ContentLength = btBodys.Length;
httpWebRequest.GetRequestStream().Write(btBodys, 0, btBodys.Length);

HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream());
string responseContent = streamReader.ReadToEnd();

httpWebResponse.Close();
streamReader.Close();
httpWebRequest.Abort();
httpWebResponse.Close();

return responseContent;
}

POST方法(httpWebRequest)

/// <summary>
/// 通过WebClient类Post数据到远程地址，需要Basic认证；
/// 调用端自己处理异常
/// </summary>
/// <param name="uri"></param>
/// <param name="paramStr">name=张三&age=20</param>
/// <param name="encoding">请先确认目标网页的编码方式</param>
/// <param name="username"></param>
/// <param name="password"></param>
/// <returns></returns>
public static string Request_WebClient(string uri, string paramStr, Encoding encoding, string username, string password)
{
if (encoding == null)
encoding = Encoding.UTF8;

string result = string.Empty;

WebClient wc = new WebClient();

// 采取POST方式必须加的Header
wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded");

byte[] postData = http://www.mamicode.com/encoding.GetBytes(paramStr);

if (!string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password))
{
wc.Credentials = GetCredentialCache(uri, username, password);
wc.Headers.Add("Authorization", GetAuthorization(username, password));
}

byte[] responseData = http://www.mamicode.com/wc.UploadData(uri,"POST", postData); // 得到返回字符流
return encoding.GetString(responseData);// 解码
}

POST方法(WebClient)

public static string GetHttp(string url, HttpContext httpContext)
{
string queryString = "?";

foreach (string key in httpContext.Request.QueryString.AllKeys)
{
queryString += key + "=" + httpContext.Request.QueryString[key] + "&";
}

queryString = queryString.Substring(0, queryString.Length - 1);

HttpWebRequest httpWebRequest = (HttpWebRequest)WebRequest.Create(url + queryString);

httpWebRequest.ContentType = "application/json";
httpWebRequest.Method = "GET";
httpWebRequest.Timeout = 20000;

//byte[] btBodys = Encoding.UTF8.GetBytes(body);
//httpWebRequest.ContentLength = btBodys.Length;
//httpWebRequest.GetRequestStream().Write(btBodys, 0, btBodys.Length);

HttpWebResponse httpWebResponse = (HttpWebResponse)httpWebRequest.GetResponse();
StreamReader streamReader = new StreamReader(httpWebResponse.GetResponseStream());
string responseContent = streamReader.ReadToEnd();

httpWebResponse.Close();
streamReader.Close();

return responseContent;
}

Get方法(HttpWebRequest)

/// <summary>
/// 通过 WebRequest/WebResponse 类访问远程地址并返回结果，需要Basic认证；
/// 调用端自己处理异常
/// </summary>
/// <param name="uri"></param>
/// <param name="timeout">访问超时时间，单位毫秒；如果不设置超时时间，传入0</param>
/// <param name="encoding">如果不知道具体的编码，传入null</param>
/// <param name="username"></param>
/// <param name="password"></param>
/// <returns></returns>
public static string Request_WebRequest(string uri, int timeout, Encoding encoding, string username, string password)
{
string result = string.Empty;

WebRequest request = WebRequest.Create(new Uri(uri));

if (!string.IsNullOrEmpty(username) && !string.IsNullOrEmpty(password))
{
request.Credentials = GetCredentialCache(uri, username, password);
request.Headers.Add("Authorization", GetAuthorization(username, password));
}

if (timeout > 0)
request.Timeout = timeout;

WebResponse response = request.GetResponse();
Stream stream = response.GetResponseStream();
StreamReader sr = encoding == null ? new StreamReader(stream) : new StreamReader(stream, encoding);

result = sr.ReadToEnd();

sr.Close();
stream.Close();

return result;
}

#region # 生成 Http Basic 访问凭证 #

private static CredentialCache GetCredentialCache(string uri, string username, string password)
{
string authorization = string.Format("{0}:{1}", username, password);

CredentialCache credCache = new CredentialCache();
credCache.Add(new Uri(uri), "Basic", new NetworkCredential(username, password));

return credCache;
}

private static string GetAuthorization(string username, string password)
{
string authorization = string.Format("{0}:{1}", username, password);

return "Basic " + Convert.ToBase64String(new ASCIIEncoding().GetBytes(authorization));
}

#endregion

basic验证的WebRequest/WebResponse

C#通过WebClient/HttpWebRequest实现http的post/get方法